In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. One of the most common approaches to achieving a low emission, high efficiency car is through the use of a hybrid drive train in which an internal combustion engine is combined with one or more electric motors. An alternate approach that is intended to reduce emissions even further while simultaneously decreasing drive train complexity is one in which the internal combustion engine is completely eliminated from the drive train, thus requiring that all propulsive power be provided by one or more electric motors. Regardless of the approach used to achieve lower emissions, in order to meet overall consumer expectations it is critical that the drive train maintains reasonable levels of performance, range, reliability, and cost.
Irrespective of whether an electric vehicle (EV) uses a hybrid or an all-electric drive train, the battery pack employed in such a car presents the vehicle's design team and manufacturer with various trade-offs from which to select. For example, the size of the battery pack affects the vehicle's weight, performance, driving range, available passenger cabin space and cost. Battery performance is another characteristic in which there are numerous trade-offs, such as those between power density, charge rate, life time, degradation rate, battery stability and inherent battery safety. Other battery pack design factors include cost, both on a per battery and per battery pack basis, material recyclability, and battery pack thermal management requirements.
In order to lower battery pack cost and thus the cost of an EV, it is critical to reduce both component cost and assembly time. An area of pack fabrication that has a large impact on assembly time, especially for large packs utilizing small form factor batteries, is the procedure used to connect the batteries together, where the batteries are typically grouped together into modules which are then interconnected within the pack to achieve the desired output power. In a conventional pack, the high current interconnects that electrically connect each terminal of each battery to the corresponding bus bar are typically comprised of wire, i.e., wire bonds. Unfortunately wire bonding is a very time consuming, and thus costly, process and one which may introduce reliability issues under certain manufacturing conditions.
Accordingly, what is needed is a robust interconnect that allows the battery pack to be quickly and efficiently assembled, thus lowering manufacturing time and cost. The present invention provides such an interconnect design and manufacturing process.